socket 实现最小化UDP广播程序

广播是某一个终端给一个子网发送数据，这个子网可以是本地的最小化子网，比如 192.168.1.255，也可以是整个子网 255.255.255.255，这取决于你要发送的范围，本文中只介绍一个最小化的广播程序，值得注意的是，即使客户端没有设定IP地址，它依然是可以接收到广播数据的。

服务端代码

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <net/if.h>

#define SERVER_PORT 8000
#define CLIENT_PORT 9000
#define MAXLINE 1500
#define BROADCAST_IP “255.255.255.255”// 广播地址

int main(void)
{
int sockfd;
struct sockaddr_in serveraddr, clientaddr;
char buf[MAXLINE] = “mycode\n”;

/\* 构造用于UDP通信的套接字 \*/
sockfd = socket(AF\_INET, SOCK\_DGRAM, 0);
bzero(&serveraddr, sizeof(serveraddr));

/* IPv4 */
serveraddr.sin_family = AF_INET;
/* 本地任意IP INADDR_ANY = 0 */
serveraddr.sin_addr.s_addr = htonl(INADDR_ANY);
serveraddr.sin_port = htons(SERVER_PORT);
bind(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr));

// 设置socket为广播方式
int flag = 1;
setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &flag, sizeof(flag));

/\*构造 client 地址 IP+端口  192.168.12.255+9000 \*/
bzero(&clientaddr, sizeof(clientaddr));
clientaddr.sin\_family = AF\_INET;
inet\_pton(AF\_INET, BROADCAST\_IP, &clientaddr.sin\_addr.s\_addr);
clientaddr.sin\_port = htons(CLIENT\_PORT);

int i = 0;
while (1) {
    sprintf(buf, "mycode %d\\n", i++);

// 发送数据
sendto(sockfd, buf, strlen(buf), 0,
(struct sockaddr *)&clientaddr, sizeof(clientaddr));
sleep(1);
}
close(sockfd);
return 0;
}

客户端代码

#include <netinet/in.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <net/if.h>
#define SERVER_PORT 8000
#define MAXLINE 4096

#define CLIENT_PORT 9000
int main(int argc, char *argv[])
{
struct sockaddr_in serveraddr, localaddr;
int confd;
ssize_t len;
char buf[MAXLINE];

//1.创建一个socket
confd = socket(AF\_INET, SOCK\_DGRAM, 0);

//2.初始化本地端地址
bzero(&localaddr, sizeof(localaddr));
localaddr.sin\_family = AF\_INET;
inet\_pton(AF\_INET, "0.0.0.0" , &localaddr.sin\_addr.s\_addr);
localaddr.sin\_port = htons(CLIENT\_PORT);

// 广播客户端也要绑定固定的端口，否则接收不到
bind(confd, (struct sockaddr *)&localaddr, sizeof(localaddr));

socklen\_t slen;
while (1) {
    slen = sizeof(serveraddr);
    len = recvfrom(confd, buf, sizeof(buf), 0, (struct sockaddr \*)&serveraddr, &slen);
    //printf("%s\\n", inet\_ntop(AF\_INET, &serveraddr.sin\_addr.s\_addr, buf, sizeof(buf)));
    write(STDOUT\_FILENO, buf, len);
}
close(confd);
return 0;

}

编译

编译客户端：gcc boardcast_client.c -o boardcast_client 编译服务端：gcc boardcast_server.c -o boardcast_server 运行效果：

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